1. Field of the Invention
The present invention relates to a light receiving element for converting a received light signal into an electric signal and a method of manufacturing the same.
2. Description of the Related Art
An optical coupling allows light signals emitted from light sources, such as a laser diode, fiber, a Planar Lightwave Circuit (PLC) device and the like, to arrive at the light receiving surface without a loss, so as to be converted into optimal electric signals. Many studies have shown that a vertical photodiode has a higher reliability than a waveguide photodiode for the provision of light signal conversion.
In order to manufacture a light module of ultra-low cost, the light module must be manufactured in complete automatization, that is, in a chip mounting method. Therefore, two-dimensional optical coupling is necessary throughout the field of optical coupling, such as optical coupling between a laser diode and a photodiode, between a fiber and a photodiode, between a PLC and a photodiode, and so forth.
FIG. 1 is a sectional view showing the structure of a photo detector for two-dimensional optical coupling according to the prior art. The photo detector is a light receiving element having the so-called edge-illuminated refracting-facet structure.
As shown, the photo detector includes: an InP substrate 1, a light-incidence plane 2, an n-type InP layer 3, a photo-absorption layer 4, a p-type InP layer 5, a p-type electrode 6, and an n-type electrode 7. The light-incidence plane 2 of the photo detector is formed so as to be inclined at an angle of θ through a wet etching process. As a result, the photo detector has a structure in which incident light is refracted to the photo-absorption layer 4. The refracted light, which is incident to the photo-absorption layer, has longer effective absorption length than that of the light being incident in a vertical direction, thus increasing the receiving sensitivity.
However, the conventional photo detector undergoes a chemical etching process for forming an angled facet. As such, the manufacturing of the photo detector according to the conventional art has drawbacks in that reproducibility and uniformity of elements are difficult to achieve. Furthermore, if an anti-reflective coating layer is implemented to improve the performance, a difficult task of mesa etching is required which in turn reduces the productive yield as it requires additional steps.